This invention is directed to a decorative multi-layer sheet and in particular to a multi-layer sheet film that has a weatherable surface layer.
A variety of processes have been developed to form decorative multi-layer sheet structures that can be molded into parts but each of these processes has problems that make the multi-layer sheet unacceptable, for example, for exterior automotive or truck use, due to wrinkles and air-pockets in the multi-layer sheet. Recycling of the multi-layer sheet material also is a problem since the fluoropolymer component of a multi-layer sheet must be separated from the thermoplastic layers of the sheet. When using reflective flakes in the colored layer of the sheet structure, such as aluminum flakes, proper orientation of the flakes must be achieved to have the desired appearance that will not occur unless proper processing conditions and polymers are used.
For example, U.S. Pat. No. 5,707,697 discloses a dry paint transfer process for forming DOI (Distinctness of Image) multi-layer sheet materials. “DOI” is a measure of the “degree of definition” of a reflection of an object in a colored finish compared to the actual object itself. DOI is defined in ASTM Standard-D5767-95 as: distinctness-of-image-gloss, n-aspect of gloss characterized by the sharpness of images of objects produced by reflection at a surface. DOI can be measured with a BYK-Gardner Wavescan DOI instrument. In the automotive industry, satisfactory finishes on a smooth or “Class A” surface typically will have a DOI value of at least 60 and preferably, 80 or higher. U.S. Pat. Nos. 4,931,324; 5,514,427; and 5,342,666 disclose processes for forming injection molded plastic articles having weatherable paint film surface. U.S. Pat. No. 5,114,789 discloses a protective and decorative sheet material having a transparent top coat. U.S. Pat. No. 6,254,712 discloses making high transparency protective and decorative films. U.S. Pat. No. 4,868,030 discloses applying a pre-painted carrier film to an automobile body. U.S. Patent Application Publication 2002/0055006 discloses multi-layer co-extruded ionomer. WO 02066249 discloses co-extruded polymeric coating. Finally WO 9841399 discloses a multi-layered polyester sheet material.
There is a need for an extrusion lamination process for forming a multi-layer sheet material wherein a weatherable clear layer is brought together with a relative low melting pigmented colored layer and an optional backing layer and the resulting multi-layer sheet under thermoforming conditions forms a part with very few imperfections and the multi-layer sheet material is recyclable since the weatherable clear layer can be readily separated from the sheet prior to a subsequent thermoforming operation.